Method for treating cracked gas oil

ABSTRACT

A concentrate of 2,6- and 2,7-dimethylnaphthalene (DMN) and a polyvinyl chloride (PVC) plasticizer is obtained from cracked gas oil (CGO) by alkylating the CGO with an olefin in the presence of an alkylation catalyst then distilling off a cut which will include the 2,6- and 2,7-DMN. In the alkylation, the other dialkylnaphthalenes which are normally difficult to separate from the 2,6- and 2,7-DMN are preferentially alkylated and end up as higher boiling materials of which a 600*-750*F. fraction is a PVC plasticizer. Thus, when a 495* to 510*F. fraction of the alkylation product is taken, it will be greatly enriched in the 2,6- and 2,7-DMN. For example, a 495*-508*F. CGO fraction is alkylated with a 50*-105*F. fraction of catalytic gasoline which contains 60% C5-olefins in the presence of a BF3/H3PO4 catalyst. The charge contained a total of 67.3% DMN (15.5% 2,6- and 14.9% 2,7-DMN) and the 495*-508*F. fraction of the alkylation product contained 52.3% total DMN (26.2% 2,6- and 25.7-DMN). This concentrate is then subjected to a further purification such as liquid extraction followed by neat crystallization. The heavy alkylated material (600*-750*F.) is a good PVC plasticizer.

United States Patent Kirk, Jr. et a].

[ 1 *Nov. 4, 1975 METHOD FOR TREATING CRACKED GAS OIL [73] Assignee: Sun Ventures, Inc., St. Davids, Pa.

[ Notice: The portion of the term of this patent subsequent to Apr. 8, 1986, has been disclaimed.

22 Filed: Nov. 20, 1973 211 App]. No.: 417,662

Related US. Application Data [63] Continuation of Ser. No. 777,244, Nov. 20, 1968, abandoned, which is a continuation of Ser. No.

627,887, April 3, 1967, abandoned.

4/1969 Kirk, Jr. et al 26053.6 UA

SEPARA CRACKED GAS on. T ON TANK Anowmc EXTRACT J 5 WASHING TANK Primary Examiner-Morris Liebman Assistant Examiner-S. L. Fox

Attorney, Agent, or FirmGe orge L. Church; J. Edward Hess; Barry A. Bisson ABSIRACT A concentrate of 2,6- and 2,7-dimethylnaphthalene (DMN) and a polyvinyl chloride (PVC) plasticizer is obtained from cracked gas oil (CGO) by alkylating the CGO with an olefin in the presence of an alkylation catalyst then distilling off a cut which will include the 2,6- and 2,7-DMN. In the alkylation, the other dialkylnaphthalenes which are normally difficult to separate from the 2,6 and 2,7-DMN are preferentially alkylated and end up as higher boiling materials of which a 600750F. fraction is a PVC plasticizer. Thus, when a 495 to 510F. fraction of the alkylation product is taken, it will be greatly enriched in the 2,6- and 2,7-DMN. For example, a 495508F. CGO fraction is alkylated with a 105F. fraction of catalytic gasoline which contains C -olefins in the presence of a BF /H PO catalyst. The charge contained a total of 67.3% DMN (15.5% 2,6- and 14.9% 2,7- DMN) and the 495-508F. fraction of the alkylation product contained'52.3% total DMN (262% 2,6- and 25.7-DMN). This concentrate is then subjected to a further purification such as liquid extraction followed by neat crystallization. The heavy alkylated material (600750F.) is a good PVC plasticizer.

13 Claims, 1 Drawing Figure INITIAL -.495 F o SYNTHETIC cnuoz 'rowsas To 2m 2w mm RECOVERY DISHLLATION 44 TOWER O 520 F ALKYLATION l i REACTOR I I A? CATALYTIC GASOLINE 5 g /4 TRAcTloM5Cf-m5"; I r DISTILLATION 4 7 Town 2 l inf-soc F RECYt-LE 22 surf-o F 75 29 PLASTICER OIL DISTILLATION TOWER r TO CARBON BLACK OIL DI STILL ATION TOWER METHOD FOR TREATING CRACKED GAS OIL This is a continuation of application Ser. No. 777,244 filed Nov. 20, 1968, now abandoned, which is a continuation of Ser. No. 627,887, filed Apr. 3, 1967, now abandoned.

' BACKGROUND or THE INvENTIoN Concentration of 2,6- and 2,7-dimethylnaphthalene is required prior to separation and purification. 2,6-and 2,7-dimethylnaphthalene is normally derived from a cracked gas oil (CGO) fraction boiling in the range of 400650F'. which contains mono-, diand trialkyl naphthalene constituents;

The synthetic fiber and film market has achieved significant importance in the commercial world. One of the more important materials from which such fibers are made and which has generated a great deal of interest is the polyester of 2,6-dicarboxynaphthalene. Similarly, interest has developed in polyesters prepared from the 2,7-dicarboxynaphthalene. Thus, 2,6- and 2,7-dimethylnaphthalene have become important precursors for oxidation to prepare the corresponding dicarboxylic acids. The principal source of these two isomers is cracked gas oil derived from petroleum. However, it has been very difficult to separate 2,6- and 2,7- dimethylnaphthalene from the cracked gas oil fraction. The separation can be simplified by concentrating these two materials initially. Subsequent highly refined separations are then more effective at'producing substantially pure isomers. I

'Some of the methods used for purifying the 2,6-and 2,7-dimethylnaphthalene are neat crystallization such as that shown in US. Pat. No. 3,207,726 to Malmberg et al.; azeotropic distillation as shown in US. Pat. No. 3,171,794 to Wynkoop et al. and extraction-azeotropic distillation as shown in US. Pat. No. 3,171,863 to Wynkoop et al.

A related problem has been to find a utility for the by-product, that is, the remaining portion of cracked gas oil from which the 2,6- and 2,7-isorners are removed. Generally it has been most expedient to return this by-product to the catalytic gas oil stream of its origin. However, it hasbeen found to be economically more desirable to further separate the cracked gas oil stream into fractions which have different and more valuable properties because of the alkylation.

One of the present by-products is a polyvinyl chloride plasticizer. There is considerableinterest in polyvinyl chloride oil plasticizers. Work to date has been directed mainly toward tailoring existing refinery streams such as heavy aromatic extracts from catalytic cracking operations for PVC plasticizers. These oils, however, are characterized by poor color stability in the presence of sunlight. The oils of the present invention have very good ultraviolet stability.

The process of the present invention can be used alone as a means of concentration and purification or more preferably in combination with subsequent purifications to achieve a high degree of 2,6- and 2,7-DMN purity.

SUMMARY OF THE INVENTION The present invention involves concentration of 2,6- and 2,7-dimethylnaphthalene from a mixture of petroleum hydrocarbons wherein the mixture is contacted with an olefinic material in the presence of an alkylation catalyst and the recovery of an alkylated fraction 2 which is a polyvinyl chloride plasticizer. In one embodiment, materials other than 2,6- and'2,7-dimethylnaphthalene are preferentially alkylated so that upon fractionation of the resulting alkylated mixture, a fraction having the same boiling range as the charge will have a higher concentration of the 2,6- and 2,7-dimethylnaphthalene than the charge. The dimethylnaphthalenes which have been alkylated remain behind as a high boiling fraction. In another embodiment, a narrower distillation cut is taken than the original charge. Preferably, this narrow cut will be in the range of 495 to 510F. A high boiling fraction from the alkylation which is composed principally of alkylnaphthalenes makes an excellent plasticizer oil for polyvinyl chloride. I

DRAWING The drawing is a schematic flow diagram of thealkylation and subsequent separation of the alkylated fractions.

DESCRIPTION OF THE INVENTION The charge material used in the present invention is obtained as a cracked gas oil fraction boiling in the range of ,400650F. which contains mono-, diand trialkylnaphthalene constituents. Within this definition of starting material are included cracked gas oils as obtained directly from distillation of cracking products such as gas oils having an initial boiling point not substantially lower than 400F. and a final boiling point not substantially higher than 650]F.; mixed aromatic concentratesobtained from such cracked gas oils and having a boiling range substantially the same as the starting cracked gas oil; and fractions separated from either of the above materials but which boil within the narrower range of 440520F. preferably 480515F. As used herein, the term cracked includes thermal, catalytic and reforming operations.

According to the present invention, the cracked petroleum fraction should contain substantial amounts of dicyclic aromatic compounds and preferably little if any tricyclic compounds. Since the petroleum fraction can be derived from any source of crude petroleum, its

specific composition can vary considerably. Thus, even though the boiling range of the petroleum fraction can be between 400 and 650F., it is preferable. that the boiling range be substantially between 440 and 520F.

and more preferably between 480515F. so that a concentrate of such dicyclic compounds as dimethylnaphthalene (DMN) can be obtained. Usually suitable charge materials within the definition of cracked gas oils will typically have an API gravity at 60F. between 12 and 40; a refractive index at 20C. of from 1.4500 to 1.5800 and a sulfur content. of from 0.5% by weight to 3.0% by weight.

A preferred CGO fraction is a dicyclic aromatic concentration. The concentrate is derived from a cracked gas oil fraction boiling mainly in the range of 440515F. This fraction is first countercurrently extracted with a furfural solvent. The extract phase is first diluted with additional furfural and then treated with a C -C saturated hydrocarbon such as hexane. The extract phase is then stripped of furfural and hexane. The remaining concentrate has a very high dicyclic aromatic content. A detailed description of this process is not necessary since the process is fully described in US. Pat. No. 3,172,919 issued Mar. 9, 1965, to Hagerty et al. v

The concentrate will contain essentially 100% of the dicyclic aromatics, less than 50% of the monocyclic aromatics and essentially none of the non-aromatics of the CO stream. This preferred CGO fraction will contain at least 75 wt. dicyclic aromatics, up to 100 wt. but in practice, the upper dicyclic aromatic content will be about 87-90 wt.

The olefinic material employed to alkylate a petroleum hydrocarbon fraction is a C to C3 olefin, a mixture of these olefins or a hydrocarbon fraction such as a 50105F. fraction of catalytic gasoline. Preferred and particularly effective are olefins which can produce tertiary carbonium ions, i.e., isobutylene. When a hydrocarbon mixture containing olefins is employed as the alkylating agent, it should contain at least wt. percent olefins. The examples presented herein were perfonned using a C fraction of catalytic gasoline boiling in the range of 50105F. and containing about 60% olefins weight.

The olefinic material is contacted with the charge material underalkylating conditions in the presence of an alkylation catalyst. A temperature of 0 to 600F., pressure of to 1500 p.s.i.a. and residence time of 5 seconds to 300 minutes is suitable depending to some degree on the particular alkylation catalyst employed, the heat transfer obtained and whether a vapor phase or liquid phase alkylation is used.

Any conventional alkylation catalysts can be used.

These include hydrofluoric acid, phosphoric acid, sulfuric acid, Friedel-Crafts catalysts such as zinc chloride, aluminum chloride, ferric chloride, boron fluoride and'the like and complexes of Friedel-Crafts catalysts with organic polar liquids such as nitrobenzene, chloroform and nitromethane. The catalyst can be unsupported or supported such as H PO on Kieselguhr. An active catalyst in the alkylation is boron trifluoride and phosphoric acid.

The polyvinyl chloride plasticizer is the alkylated fraction boiling between 600 and 750F. and preferably between 650 and 720F.

Referring now to the drawing which is a schematic representation of an alkylation and separation of the alkylated products, a dicyclic aromatic extract from cracked gas oil (87.7% dicyclic aromatics) having a boiling range of 440520F. line 1 is premixed with a C catalytic gasoline fraction boiling in the range of 50-105F. from line 2 and passed through line 3 into the alkylation reactor 4 which contains BF3/H3PO4 (0.2

to 1.7 mole ratio saturation limit) added through line 5. The reactor is maintained at a temperature of about 60F. and a reactant residence time of 1 minute. The alkylated mixture passes from reactor 4 through line 6 into separation tank 7 where water'is added through line 8 to deactivate the catalyst. Water and catalyst are removed through line 9 and the product passes through line 10 into washing tank 11 where an aqueous solution of sodium bicarbonate is added through line 12 to wash the alkylated product. The wash solution is removed through line l3.-The alkylate product passes through line 14 intodistillation tower 15 where the material boiling below 495F. is taken off and sent through line 16 to synthetic crude towers (not shown) for further processing. The bottoms from distillation column 15 are sent through line 17 to distillation tower 18 wherein the 2,6- and 2,7-DMN fraction is, distilled off at 495-510F. and removed through line 19. Thisfraction contains about 2,6- and 2,7-DMN of which 25-28% is 26- isomer and can be used in some polymerizations but more preferably is subject to further separations such as those shown in the previously mentioned US. patents, i.e., combined solvent extractionazeotropic distillation, azeotropic distillation and neat crystallization. The bottoms from distillation tower- 18 pass through line 20 to distillation tower 21 where the fraction boiling between 510 and 600F. is recycled through line 22 to line 3 for further treatment in the alkylation reactor. The bottoms from distillation tower 21 pass through line 23 into distillation tower 24 where the material boiling between 600 and 750F. is taken off through line 25. This material is an excellent plasticizer for PVC. The-bottoms from distillation tower 24 are withdrawn through line 26 and are suitable carbon black oil blend stock.

EXAMPLES 1 and 2 Following a procedure such as set out above in the description of the drawing, a dicyclic aromatic concentrate, which was derived from CGO in accordance with the procedure of US. Pat. No. 3,172,919 discussed above, boiling in the range of 440 to 520F. and a 495-508F. portion of this aromatic concentrate were each charged to the alkylation reactor using the BF /H PO alkylation catalyst. Table 1 shows in weight percent the constitution of the charge prior to alkylation and the constitution of the alkylation product determined by vapor phase chromatography and infrared analysis. Table 11 shows the weight and volume of the charge and the products in terms of boiling ranges.

TABLE 1 Values in Weight Percent EXAMPLE 2 CHARGE PRODUCT CHARGE PRODUCT 440-520F. 440-5 20F. 495508F. 495-508F. boiling range boiling cut of Ex.l boiling arom. conc. range charge range VPC/lR: (wt.

naphthalene 5.3 0 0 methylnaphthale ne 27 .5 3 .8 4.8 ethylnaphthalene 4.1 I 0.4 6.6 DMN (total) 50.8 31.1 67.3 52.3 2.6-DMN 9.8 14.1 15.5 26.2 2,7-DMN 7.7 12.1 14.9 25.7 other DMN isomers 33.3 4.9 36.9 .4 C 6.4 1.1 0.3 other 5.9 636* 17.0 4 .7

2.6-+2.7-DMN total DMN 7: 34.5 84.2 45.2 99.3 ratio:

2,6-DMN 2,7-DMN 1.27 1.17 v 1.04 1.02

Total DMN TABLE I-continued a Valuesin-Weight Percent EXAMPLE I v l y 2 A CHARGE PRODUCT CHARGE PRODUCT 440-5 F. 440-5 20F. 4Q5,.508F. -495508F. boiling range boiling cut of Ex.l boiling arom. conc. range charge range Converted I 78% 85% Reaction Temp. F.' I40 60 charge molematio olefin aromatic 1.2 3 .8 Time (hours) 2.5 3.0" J BF II-I PO mole ratio l.7 1.7 catalyst/reactant weight ratio 0.4 0.4

37.4 aromatics; 26.2 olefins saturates "*l9.l aromatics: 28.6 olefins saturates Examples 1 and 2 show products which are the same boiling range as their charge. Both examples show a marked concentration of the 2,6- and 2,7-DMN as opposed to the other naphthalenes of the fraction. The concentrated fraction is now suitable for subsequent treatment to purify the 2,6- and 2,7-DMN and the alkylated by-product boiling in the range of 600750F. can be used as plasticizers for polyvinyl chloride and have excellent compatibility therewith.

EXAMPLE 3 A sample of each of the plasticizers of Examples 1 and 2 and a control PVC plasticizer which was produced by hydrotreating and distilling (455 to 750F.) aromatic extract from synthetic tower bottoms from catalytic cracking was subjected to 125 hours under a sunlamp then the color measured ac- A portion of the plasticizer oil of Example 2 and the control oil of Example 3 was blended along with a primary ester (DOP) in polyvinyl chloride. The formula used for mixing with the polyvinyl chloride was as follows.

PVC 4 58.60 Lead Carbonate 0.95 Stearic Acid 0.45 Dioctylphthalate (DOP) 20.00 Plasticizer 20.00

Total 100.00

The dry ingredients were blended in a ball mill. Plasticizer was added until the mixture was wet. The mixture was put on a mill and milled for five minutes at 2903l0F., with alternate cutting. Film was sheeted Table 4 Plasticizer Example 2 Control Heat Stability hours to brittle at 300F.

U. V. Stability 24 hours (ASTM D925-) Color cream brown The invention claimed is:

1. A polyvinyl chloride composition comprising a major amount of polyvinyl chloride and a minor amount of a plasticizer composition comprising a fraction boiling within the range of 600 to 750F. prepared by the process of:

(a) contacting a cracked gas oil boiling substantially in the range of 400 to 650F. with a C to C olefinic material in the presence of an alkylation catalyst and (b) recovering the fraction boiling in the range of 600 to 750F. I

2. A polyvinyl chloride composition according to claim 1 wherein the plasticizer boils within the range of 650 to 720F.

3. A polyvinyl chloride composition according to claim 1 wherein said C to C olefinic material is a 50 to 105F fraction of catalytic gasoline.

4. A polyvinyl chloride composition according to claim 3 wherein said fraction of catalytic gasoline contains at least percent C olefins.

5. A polyvinyl chloride composition according to claim 1 wherein said cracked gas oil boiling substantially in the range of 400 to 650F is a dicyclic aromatic concentrate derived from a cracked gas oil fraction boiling mainly in the range of 440 to 515F.

6. A polyvinyl chloride composition according to claim 5 wherein said concentrate is derived by furfural extraction of said cracked gas oil fraction boiling mainly in the range of 440 to 515F.

7. A polyvinyl chloride composition according to claim 6 wherein said plasticizer composition comprises alkylated dimethylnaphthalenes.

7 8. A polyvinyl chloride composition according to claim 7 wherein the alkylated dimethylnaphthalene contains at least one alkyl group in the C to C range. 9. A polyvinyl chloride composition according to claim 8 wherein at least one said alkyl group is isobutyl. 10. A polyvinyl chloride composition according to claim 8 wherein the alkyl group other than methyl of said alkylated dimethylnaphthalene consists of C alkyl. 11. A polyvinyl chloride composition according to claim 1 wherein said composition has a lower ASTM D-l500 color after 125 hours of exposure under a sunlamp than does a control composition after said exposure, wherein said control composition contains a plasposure to heat. 

1. A POLYVINYL CHLORIDE COMPOSITION COMPRISING AMAJOR AMOUNT O POLYVINYL VHLORIDE AND A MINOR AMOUNT OF A PLASTICIZER COMPOSITION COMPRISING A FRACTION BOILING WITHIN THE RANGE OF 600* TO MK/*F. PREPARED BY THE PROCESS OF: (A) CONTACTING A CRACKED GAS OIL BOILING SUBSTASNTIALY IN THE RANGE OF 400* TO 650*F. WITH A C3 TO C8 OLEFINIC MATERIAL IN THE PRESENCE OF AN ALKYLATION ATALYST AND (B) RECOVE
 2. A polyvinyl chloride composition according to claim 1 wherein the plasticizer boils within the range of 650* to 720*F.
 3. A polyvinyl chloride composition according to claim 1 wherein said C3 to C8 olefinic material is a 50* to 105*F fraction of catalytic gasoline.
 4. A polyvinyl chloride composition according to claim 3 wherein said fraction of catalytic gasoline contains at least 60 percent C5 olefins.
 5. A polyvinyl chloride composition according to claim 1 wherein said cracked gas oil boiling substantially in the range of 400* to 650*F is a dicyclic aromatic concentrate derived from a cracked gas oil fraction boiling mainly in the range of 440* to 515*F.
 6. A polyvinyl chloride composition according to claim 5 wherein said concentrate is derived by furfural extraction of said cracked gas oil fraction boiling mainly in the range of 440* to 515*F.
 7. A polyvinyl chloride composition according to claim 6 wherein said plasticizer composition comprises alkylated dimethylnaphthalenes.
 8. A polyvinyl chloride composition according to claim 7 wherein the alkylated dimethylnaphthalene contains at least one alkyl group in the C3 to C8 range.
 9. A polyvinyl chloride composition according to claim 8 wherein at least one said alkyl group is isobutyl.
 10. A polyvinyl chloride composition according to claim 8 wherein the alkyl group other than methyl of said alkylated dimethylnaphthalene consists of C4 alkyl.
 11. A polyvinyl chloride composition according to claim 1 wherein said composition has a lower ASTM D-1500 color after 125 hours of exposure under a sunlamp than does a control composition after said exposure, wherein said control composition contains a plasticizer produced by distilling, in the range of 455* to at least 750*F, a hydrotreated aromatic extract from synthetic tower bottoms from catalytic cracking of gas oil.
 12. A polyvinyl chloride composition according to claim 11 wherein said composition and said control composition contain an ester plasticizer.
 13. A polyvinyl chloride composition according to claim 12 wherein said ester plasticizer is dioctylphthalate and wherein after exposure to a temperature of 300*F for at least three hours said control composition is more brittle than said composition after the same exposure to heat. 